Another design issue impacting compressor capacity is compressor redundancy, which has frequently been achieved in water cooled chiller systems by installing multiple single compressor chillers.
Although actual chiller design conditions for both air and water cooled chillers vary widely based on actual atmospheric and system application conditions, the standard rating conditions specified for both air and water cooled chillers in the AHRI standard 551/591 can be used as representative of common rating conditions.
To arrive at design conditions for comparison, the following two evaporator types are chosen as representative of those commonly used in air and water cooled chillers respectively.
For this analysis the lift of the water cooled chiller is 35/63 ([degrees]K/[degrees]F) and, as expected, the lift is considerably higher for the ACPC at 48/86.4 ([degrees]K/[degrees]F).
Since R-134a is currently a widely used refrigerant in air and water cooled chillers in capacities above 700 kW (199 tons) it will be used as the basis of this comparison.
The impeller diameters are now a more reasonable diameter for modern turbo machinery design and compressors of this general size are common in water cooled chillers.
A compressor mounted VFD is used to provide the same soft start, capacity modulation, and energy savings associated with VFDs when applied to centrifugal compressors on water cooled chiller systems.
Awada says: "Fresh air is introduced to the building via three fresh air handling units to improve the indoor air quality, which comprises of a heat wheel recovery wheel and run around heat pipe air handling units located on the roof and provided by chilled water via two small dedicated water cooled
chillers of 70 tons each."
Supplies central and portable chillers (both air-and water cooled
) as well as oil-and hot-water temperature controllers, negative-pressure units, cooling towers, pump-tank stations, heat exchangers,water filters, and water-treatment systems.